1. Field of the Invention
The present invention relates to a pneumatic tire, which includes a tread portion formed with a main groove extending in a circumferential direction of the tire, the main groove provided on a groove bottom with a wear indicator protruding by a predetermined height, and a tire vulcanizing die therefor.
2. Description of the Related Art
In a pneumatic tire, in order to indicate that tire replacement timing has reached due to wear, in a main groove extending in a circumferential direction of the tire, a plurality of wear indicators is disposed on the groove bottom so as to protrude therefrom at intervals in the circumferential direction of the tire. Generally, the tread portion of the pneumatic tire is formed to have a substantially same thickness as viewed in the width direction of the tire. However, in the vicinity of the wear indicator, compared to other portions, a larger amount of rubber is required in order to form the wear indicator. This causes a shortage of rubber in the vicinity of the wear indicator. As a result, a shortage of rubber occurs to cause a “light” in a wear indicator 20 itself, at edge portions E and surfaces S of a land portion located in the vicinity of the wear indicator 20 as shown in FIG. 7.
As a method to prevent the light from occurring, Japanese Unexamined Patent Publication No. 2006-88585 describes a molding and vulcanizing method of a pneumatic tire using a tire vulcanizing die. In the method, compared to other portions to be vulcanized, a larger number of vent holes are provided in a portion in the vicinity of a wear indicator. However, in the tire vulcanizing die used in such a method, a considerably large number of vent holes has to be formed. Therefore, there arises a problem that a larger man-hour is required for manufacturing the die.
Japanese Unexamined Patent Publication No. 2002-225514 describes a pneumatic tire. In the pneumatic tire, concave portions are formed on both groove walls of a main groove as viewed in a width direction of the groove, where wear indicators are disposed at intervals in a circumferential direction of the tire. Further, Japanese Unexamined Patent Publication No. 2006-205824 describes a pneumatic tire. In the pneumatic tire, concave portions, which have a streamlined-shape as viewed from the top, are formed on side walls of a main groove straightly extending as viewed from the top of a tread portion. However, any of these pneumatic tires described in these publications are not designed for preventing occurrence of a light. Therefore, a light is not prevented from occurring in the vicinity of wear indicators.